Side weirs, a delivery nozzle or nozzles, a tundish and the like installed on a casting roll unit in a twin-roll caster are members in direct contact with molten metal so that they need to be preheated before start of casting.
Thus, JP 06-339753 A discloses techniques for preheating side weirs, a delivery nozzle and a tundish to be installed on a casting roll unit before start of casting.
A twin-roll caster in JP 06-339753 A will be outlined with reference to FIGS. 1–4. This device comprises, as shown in FIG. 2, a casting roll unit U having two water-cooled, contra-rotatable parallel casting rolls 1 which are supported by a carriage frame 3 of a casting roll carriage 2. The casting roll carriage 2, which supports the casting roll unit U, is adapted to be displaced between an assembly station B and an actual casting station A in a lateral direction perpendicular to a widthwise direction of the roll unit U or to a lengthwise direction of the casting rolls 1.
Side-weir mounting/dismounting devices 4 shown in FIG. 4 are arranged widthwise outward of the casting roll unit U when the roll unit is at the casting station A. Each of the side-weir mounting/dismounting devices 4 comprises a hydraulic cylinder unit 5a and a plate holder 5b movable in the above-mentioned widthwise direction by actuating the hydraulic cylinder unit 5a. Side weirs 6 are mounted on the plate holders 5b and urged by the expanded cylinder units 5a into engagement with opposite stepped ends 7 of the casting rolls 1 to thereby close the opposite ends of the casting rolls 1.
A tapered delivery nozzle 8 is arranged above and between the casting rolls 1, and is long in the widthwise direction to provide an inwardly and downwardly converged bottom as shown in FIG. 3 to fit into a mounting bracket 9 on the carriage frame 3 of the roll carriage 2, thereby entering into a nip between the parallel casting rolls 1.
Furthermore, a tundish 10 is positioned via its mounting bracket 11 on the carriage frame 3 of the roll carriage 2.
A ladle 12 (FIG. 1) is adapted to be positioned above the casting roll unit U at the casting station A and to supply molten metal via the tundish 10 and delivery nozzle 8 during casting. Thus, furnaces to preheat the side weirs 6, delivery nozzle 8 and tundish 10 and robot devices to displace them are arranged at positions not interfering with the ladle 12.
More specifically, electric resistance heater furnaces 13 are arranged above the cylinder units 5a for movement of the plate holders 5b of the side-weir mounting/dismounting devices 4 at the casting station A in FIG. 4. Side-weir robot devices 14 are arranged above and between the heater furnaces 13 and widthwise ends of the roll units U, respectively. Each of the robot devices 14 comprises, as shown in FIGS. 2 and 4, a telescopic unit 18 fixed to an upper member of a main machine frame 15 and vertically expanded or contracted by cylinder units 16 and 17, a rotary head 19 on a lower end of the telescopic unit 18 and horizontally rotatable over 180° by actuation of an air motor and a clamp mechanism 20 carried on a bottom of the rotary head 19.
As shown in FIGS. 1 and 2, a ceiling rail 21 is arranged on the upper member of the main machine frame 15 at the assembly station B to extend parallel to the widthwise direction of the casting roll unit U. A nozzle preheating furnace 22 is installed below an end of the ceiling rail 21 to preheat the delivery nozzle 8. A gas furnace 23 is installed below the other end of the ceiling rail 21 so as to preheat the tundish 10.
A telescopic, nozzle robot device 25 is arranged on the ceiling rail 21 above the nozzle preheating furnace 22 and has a clamp mechanism 24 at its lower end. Arranged on the ceiling rail 21 above the gas furnace 23 is a tundish robot device 26 (particulars thereof not shown) which can be lifted up and down while supporting the tundish 10. In FIG. 1, reference numeral 27 denotes a receptacle adjacent to the casting station A and to which the molten metal is transferred when it overflows through an overflow port 10a of the tundish 10 (FIG. 3) or when an emergency plug 10b is drawn out because of, for example, extreme deformation of a strip during a casting operation. Lift-up of a stopper rod 12a causes the ladle 12 to supply the molten metal via an outlet nozzle 12b and a refractory shroud 28 to the tundish 10.
Casting in accordance with a twin-roll caster with the above-mentioned construction will be conducted as follows.
Before starting of a casting operation, the side weirs 6, delivery nozzle 8 and tundish 10 are preheated by the furnaces 13, 22 and 23, respectively; and the casting roll unit U is displaced to the assembly station B. All the tundish 10, delivery nozzle 8 and side weirs 6 are preheated to use temperature which is, in the case of iron casting, on the order of 1200–1300° C.
The nozzle robot device 25 is displaced to above the nozzle preheating furnace 22 and is expanded to clamp the delivery nozzle 8 preheated in the nozzle preheating furnace 22, through the clamp mechanism 24. Then, the nozzle robot device is contracted and runs along the ceiling rail 21 to a position of the casting roll unit U where the nozzle robot device 25 is expanded to position the delivery nozzle on and in the mounting bracket 9 of the carriage frame 3 of the casting roll carriage 2. Then, the clamp mechanism 24 is released and the nozzle robot device 25 is contracted and runs toward the nozzle preheating furnace 22 into a stand-by position.
Next, the tundish robot device 26 is displaced to above the gas furnace 23 and is expanded to bear the tundish 10 preheated in the gas furnace 23. Then, the robot device is contracted and runs along the ceiling rail 21 to the position of the casting roll unit U where the tundish robot device 26 is expanded to position and fix the tundish 10 via its mounting bracket 11 on and to the carriage frame 3 of the casting roll carriage 2. Then, the tundish robot device 26 is contracted to be withdrawn toward the gas furnace 23 into a stand-by position.
Then, the casting roll unit U with the delivery nozzle 8 and tundish 10 is displaced from the assembly station B to the casting station A.
With the rotary heads 19 being rotated such that the clamp mechanisms 20 of the side-weir robot devices 14 at the widthwise opposite ends of the casting roll unit U are directed to the corresponding heater furnaces 13, the side-weir robot devices 14 are expanded to clamp the side weirs 6 preheated in the heater furnaces 13 through the clamp mechanisms 20; then, the side-weir robot devices 14 are contracted to take the side weirs 6 out of the heater furnaces 13. The clamp mechanisms 20 are then rotated over 180° by the rotary heads 19 and the side-weir robot devices 14 are expanded to locate the side weirs 6 on the plate holders 5b of the side-weir mounting/dismounting devices 4; and the clamp mechanisms 20 are released and the side-weir robot devices 14 are contracted, which leaves the side weirs 6 on the plate holders 5b. The hydraulic cylinder units 5a are then expanded to engage the side weirs 6 with the opposite stepped ends 7 of the casting rolls 1 of the casting roll unit U positioned at the casting station A, thereby closing the opposite ends of the casting rolls 1.
With the casting rolls 1 being rotated while being water-cooled, the ladle 12 is displaced to above the tundish 10; and lift-up of the stopper rod 12a causes the molten metal to flow from the ladle 12 via the outlet nozzle 12b and refractory shroud 28 to the tundish 10 so that the molten metal is supplied via the delivery nozzle 8 to between the casting rolls 1; and shells solidify on the casting rolls 1 into the nip, resulting in a solidified strip produced at roll exit.
However, in the conventional apparatus shown in FIGS. 1–4, first of all, the casting roll unit U is displaced to the assembly station B. Installed on the casting roll unit U are the preheated delivery nozzle 8 through running and expansion/contraction of the nozzle robot device 25 as well as the preheated tundish 10 through running and expansion/contraction of the tundish robot device 26. Then, the roll unit U is displaced from the assembly station B to the casting station A where the preheated side weirs 6 are installed on the plate holders 5b of the side-weir mounting/dismounting device 4 through expansion/contraction of the side-weir robot device 14 and rotation of the rotary heads 19. Thus, the conventional apparatus is problematic or disadvantageous in that displacement motions of the respective preheated members or delivery nozzle 8, tundish 10 and side weirs 6 become complicated and require much time for such series of operations, that the entire apparatus becomes complicated and large-sized and that position control is much troublesome since a great number of limit switches are required for controlled decelerations of the respective preheated members so as to accurately position the same.
Moreover, as mentioned above, much time is required until installation of all the preheated members on the casting roll unit U is completed, which will result in a problem that especially the side weirs 6 and delivery nozzle 8 which are less voluminous than the tundish 10 tend to become low-temperatured before such completion of the installation. In particular, structurally, installation of the delivery nozzle 8, which is installed on the casting roll unit U at the assembly station B, must precede that of the tundish 10. That is, in the conventional construction, the preheated members are installed in a specific order and the delivery nozzle 8 must be arranged first. In other words, the delivery nozzle 8, which is less voluminous, has to await the installation of the side weirs 6 being completed, leading to a problem that the nozzle is allowed to cool and the molten metal may solidify in the delivery nozzle 8.
In order to overcome such problem in particular, temperature lowering of the delivery nozzle 8 must be taken into account to preheat the delivery nozzle 8 to a temperature by far higher than that of the molten metal, which may lead to a fact that much time is needed for the preheating and consumed energy is increased. There may be also a problem of deteriorated strength of the nozzle due to extreme high-temperature heating.
The present invention was made in view of the above-mentioned conventional problems. An object of the invention is to provide an apparatus for displacing preheated members for a twin-roll caster that is simple in structure and that can promptly install preheated side weirs and delivery nozzle or nozzles on a casting roll unit.